The amount of data traffic exchanged between wireless communication devices continues to grow rapidly. The ever-increasing traffic loads lead to a pressing need for additional spectral resources of cellular systems. In order to meet the capacity requirements caused by the increase in data traffic, operators are deploying more small cells and utilizing all available spectrum resources. While mobile broadband in licensed spectrum is highly efficient due to its exclusive occupancy of the spectrum, the amount of available licensed spectrum can be limited and costly. Bandwidth-rich unlicensed spectrum can be used to effectively augment the capacity.
LTE is currently among the most advanced mobile telecommunication technologies. LTE operating in licensed spectrum is prominently deployed across the world. To further expand LTE capacity to meet growing traffic demands, developers are looking to integrate unlicensed carriers into LTE systems by adapting LTE air interfaces to operate in the unlicensed spectrum. This is often referred to as Unlicensed LTE (U-LTE), or LTE License Assisted Access (LTE-LAA).